System and method for transmitting communication signals to an automated robotic device in a data storage system

ABSTRACT

A system and method for transmission of communication signals between a controller and a robotic device in a data storage library. The system and method include a substantially planar electrical insulator having opposed first and second sides, and first and second substantially planar oppositely charged electrical conductors on the first and second sides of the insulator for use in providing electrical power to the robotic device. The system and method also include circuitry for generating the communication signals for transmission between the controller and the robotic device on one of the first and second conductors. The width of the second conductor is less than the width of the first conductor and the second conductor is substantially centered on the second side of the insulator relative to the width of the first conductor to reduce fringing of an electromagnetic field resulting from a transmitted communication signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application Ser.No. 60/302,248 filed Jun. 29, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the transmission ofcommunication signals in a data storage system and, more particularly,to a system and method for transmitting communication signals between acontroller and an automated robotic device in a tape cartridge librarysystem.

2. Background

Current automated libraries for tape cartridges typically include arraysof multiple storage cells housing the tape cartridges, as well asmultiple media drives. Multiple automated robotic devices may be used tomove tape cartridges between the various storage cells and media driveswithin a library.

The use of multiple robotic devices in automated tape cartridgelibraries raises various problems concerning the distribution of powerto such robotic devices. More particularly, robotic devices used inautomated tape cartridge libraries require power for operation thereof.In prior art automated tape cartridge libraries, the movement of therobotic devices is restricted by wire cable connections used forproviding such power. That is, such cabling can prevent the roboticdevices from crossing paths, or from continuous movement in onedirection around the library without the necessity of ultimatelyreversing direction.

Such problems can be overcome through the use of brush/wiper technology.A robotic device traveling over a given route may use a powerdistributor such as fixed conductive strips to supply power to therobotic device, which itself is provided with brushes or wipers thatcontact the conductive strips in order to conduct power to the roboticdevice. Multiple brushes are preferably used on each robotic device toimprove robustness and reliability. The integration of such conductivestrips into the automated tape cartridge library, in conjunction withbrush contacts provided on the robotic devices, allows for greaterfreedom of movement of the robotic devices, as well as for modular andextensible power distribution to robotic devices as libraryconfigurations change, or as libraries are connected in a modularfashion to form library systems.

Advantageously, the oppositely charged conductive layers of a powerstrip as described above can be used for transmitting communicationsignals between the robotic device and a host controller. In doing so,however, electromagnetic interference and unintended signal emissionscan be a problem. This can be particularly true for power conductorsthat are quite long. Interference from radio, television, and otherradio frequency (RF) electromagnetic radiation sources, whether or notintentionally emitted, can interfere with the communication signalsmodulated onto the power conductors. Such interference can cause datatransmission errors and slow the maximum attainable rate of datatransfer.

In that same regard, when communication signals are modulated onto along power conductor, some of the RF energy can radiate through the airand interfere with nearby independent power conductors. If the nearbypower conductors also contain modulated communication signals, harmfulinterference can result. The energy radiated by the modulated powerconductors may also cause interference in radio and television broadcastbands, or other restricted RF bands. Such interference may be prohibitedby government regulations.

Thus, there exist a need for an improved system and method fortransmitting communication signals between a controller and a roboticdevice in a data storage library. Such a system and method would improvethe electromagnetic compatibility (EMC) of brush and strip powerdistribution by the orientation of the power strip conductors. Moreparticularly, such an improved system and method would employ positiveand negative (ground) conductors preferably separated by a thin layer ofinsulating dielectric. The positive conductor would preferably becentered over the negative conductor, and the negative conductor wouldpreferably be wider than the positive conductor in order to minimizefringing of the electric filed due to the modulated communicationsignal. The thin dielectric would minimize the “loop area” of theconductors. The conductors themselves would be substantially flat andrelatively thin in order to reduce their respective surface areas,thereby reducing “skin effect.”

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an improved system andmethod for transmitting communication signals to and from an automatedrobotic device for use in a data storage library.

According to the present invention, then, in a data storage libraryhaving a plurality of cells for holding media cartridges for use instoring data, at least one media drive, a robotic device fortransporting cartridges between the plurality of cells and the at leastone media drive in the data storage library, and a controller forcontrolling the robotic device, a system is provided for transmission ofcommunication signals between the controller and the robotic device. Thesystem comprises a substantially planar electrical insulator havingopposed first and second sides, a first substantially planer electricalconductor on the first side of the insulator for use in providingelectrical power to the robotic device, the first conductor to beprovided with an electrical charge and having a width, and a secondsubstantially planar electrical conductor on the second side of theinsulator for use in providing electrical power to the robotic device,the second conductor to be provided with an electrical charge oppositethe electrical charge of the first conductor, the second conductorhaving a width. The system further comprises means for generating thecommunication signals for transmission between the controller and therobotic device on one of the first and second conductors, wherein thewidth of the second conductor is less than the width of the firstconductor, and the second conductor is substantially centered on thesecond side of the insulator relative to the width of the firstconductor to reduce fringing of an electromagnetic field resulting froma transmitted communication signal.

Also according to the present invention, in a data storage libraryhaving a plurality of cells for holding media cartridges for use instoring data, at least one media drive, a robotic device fortransporting cartridges between the plurality of cells and the at leastone media drive in the data storage library, and a controller forcontrolling the robotic device, a method is provided for transmission ofcommunication signals between the controller and the robotic device, themethod comprises providing a substantially planar electrical insulatorhaving opposed first and second sides, providing a first substantiallyplaner electrical conductor on the first side of the insulator for usein providing electrical power to the robotic device, the first conductorto be provided with an electrical charge and having a width, andproviding a second substantially planar electrical conductor on thesecond side of the insulator for use in providing electrical power tothe robotic device, the second conductor to be provided with anelectrical charge opposite the electrical charge of the first conductor,the second conductor having a width. The method further comprisesproviding means for generating the communication signals fortransmission between the controller and the robotic device on one of thefirst and second conductors, wherein the width of the second conductoris less than the width of the first conductor, and the second conductoris substantially centered on the second side of the insulator relativeto the width of the first conductor to reduce fringing of anelectromagnetic field resulting from a transmitted communication signal.

The above features, and other features and advantages of the presentinvention are readily apparent from the following detailed descriptionsthereof when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a robotic device for use in an automatedtape cartridge library having brush and strip power distribution;

FIGS. 2a and 2 b are partial cross-sectional views of a robotic devicefor use in an automated tape cartridge library having brush and strippower distribution;

FIG. 3a is a simplified block diagram of a robotic device for use in anautomated tape cartridge library according to the prior art;

FIG. 3b is a simplified a block diagram of a robotic device for use inan automated tape cartridge library having brush and strip powerdistribution;

FIGS. 4a and 4 b are simplified overhead block diagrams of a power stripand robotic device with conductive brushes for use in an automated tapecartridge libraries;

FIGS. 4c and 4 d are simplified electrical schematics depicting powersupply redundancy schemes according to the present invention;

FIG. 5 is a perspective view of a robotic device for use in an automatedtape cartridge library having brush and wheel power distribution;

FIG. 6 a more detailed perspective view of a robotic device for use inan automated tape cartridge library having brush and wheel powerdistribution;

FIG. 7 is another more detailed perspective view of a robotic device foruse in an automated tape cartridge library having brush and wheel powerdistribution;

FIGS. 8a and 8 b are side and cross-sectional views, respectively, of abrush and wheel mechanism for power distribution to a robotic device inan automated tape cartridge library;

FIG. 9 is an exploded perspective view of power strip and guide railjoint for use in an automated tape cartridge library;

FIG. 10 is a perspective view of a power strip joint for use in anautomated tape cartridge library;

FIGS. 11a and 11 b are additional perspective views of a power stripjoint for use in an automated tape cartridge library;

FIGS. 12a and 12 b are perspective views of a guide rail sections foruse in an automated tape cartridge library having brush and strip powerdistribution;

FIGS. 12c-g are cross-sectional and side views of a power strip andguide rail assembly for use in an automated tape cartridge library;

FIG. 13 is a simplified block diagram illustrating distribution ofcommunication signals to and from robotic devices for use in anautomated tape cartridge library according to the present invention;

FIG. 14 is a cross-sectional view of a power strip and conductivebrushes for use in an automated tape cartridge library according to thepresent invention;

FIG. 15 is a top view of a power strip for use in an automated tapecartridge library according to the present invention;

FIGS. 16a and 16 b are a cross-sectional view and a simplifiedelectrical schematic, respectively, of a power strip for use in anautomated tape cartridge library according to the present invention;

FIG. 17 is a simplified electrical schematic diagram illustrating atermination scheme for a line in a power strip or rail communicationsystem according to the present invention;

FIG. 18 is a simplified, exemplary flowchart depicting the method of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

With reference to the Figures, the preferred embodiments of the presentinvention will now be described in greater detail. The presentapplication incorporates by reference herein commonly owned U.S. patentapplication Ser. Nos. 10/033,867, 10/034,972, 10/033,944, 10/034904, andall filed on the same date as the present application.

As previously noted, current automated libraries for tape cartridgestypically include arrays of multiple storage cells housing the tapecartridges, as well as multiple media drives. Multiple automated roboticdevices may be used to move tape cartridges between the various storagecells and media drives within a library.

As also noted previously, the use of multiple robotic devices inautomated tape cartridge libraries raises various problems concerningthe distribution of power to such robotic devices. More particularly,robotic devices used in automated tape cartridge libraries require powerfor operation thereof. In prior art automated tape cartridge libraries,the movement of the robotic devices is restricted by wire cableconnections used for providing such power. That is, such cabling canprevent the robotic devices from crossing paths, or from continuousmovement in one direction around the library without the necessity ofultimately reversing direction.

Such problems can be overcome through the use of brush/wiper technology.A robotic device traveling over a given route may use a powerdistributor such as fixed conductive strips or rails to supply power tothe robotic device, which itself is provided with brushes or wipers, orwheels and brushes that contact the conductive strips or rails in orderto conduct power to the robotic device. Multiple brush or wheel pairsare preferably used on each robotic device to improve robustness andreliability. The integration of such power distributors, which also maybe referred to as power distribution strips or power distribution railassemblies, into the automated tape cartridge library, in conjunctionwith brush or wheel contacts provided on the robotic devices, allows forgreater freedom of movement of the robotic devices, as well as formodular and extensible power distribution to robotic devices as libraryconfigurations change, or as libraries are connected in a modularfashion to form library systems.

FIGS. 1 and 2a-b show perspective and cross-sectional views,respectively, of a robotic device for use in an automated tape cartridgelibrary having brush and strip power distribution. As seen therein, amoveable robotic device (20), which may be referred to as a “handbot” or“picker,” is supported by a guide structure or rail (2) preferablyhaving an integrated power strip (1). Guide rail (2) and/or power strip(1) may also be referred to as a track. Power strip (1) preferablycomprises back-to-back conductive surfaces (1A, 1B), preferably copper,separated by a dielectric (preferably FR4) in a sandwich-likeconfiguration. As described in greater detail below, such aconfiguration provides for improved impedance control. Power strip (1)may be a printed circuit board wherein copper conductors are laminated,glued or etched onto a substrate material. Alternatively, power strip(1) may comprise copper foil tape glued or laminated onto plasticmaterial, or copper inserts molded into a moldable plastic material. Anyother methods of construction or configurations known to those ofordinary skill may also be used.

Robotic device (20) includes brush contacts (6) for providing power torobotic device (20). In that regard, the back-to-back conductivesurfaces (1A, 1B) of power strip (1) are oppositely charged. An upperbrush (6A) in contact with one conductive surface (1A), in conjunctionwith a corresponding lower brush (6B) in contact with the oppositeconductive surface (1B) thereby supply power to the robotic device (20).Brushes (6) are contained in housing assembly (7) and, to ensure thatcontact between brushes (6) and power strip (1) is maintained, brushes(6) are spring loaded (8). Multiple or redundant pairs of such upper andlower brushes (6) are preferably provided, and preferably spring loaded(8) independently, to improve robustness and reliability in the event ofa brush failure, momentary loss of contact at one or more brushes due toany track irregularities, including seams or joints therein, or voltageirregularities between adjacent power strips (1). Moreover, brushes (6)preferably have a circular cross-section, such as is provided by acylindrical shaped brush (6), as these are better able to traverse ajoint or seam (38) in the power strip (1), which may more readily impedeor catch a square shaped brush.

Power supplied to robotic device (20) through power strip (1) andbrushes (6) powers a motor (not shown) in robotic device (20), which inturn drives a belt and gear system (22). Guide rails (2) includes teeth(24) which cooperate with belt and gear system (22) to permit roboticdevice (20) to move back and forth along guide rails (2) via guidewheels (26). In that regard, it should be noted that power strip (1)preferably provides DC power to robotic device (20). As seen in FIG. 1,robotic device (20) may thereby gain access to tape cartridges stored inlibrary cells (28) located adjacent guide rail (2). It should also benoted that while only a single robotic device (20) is depicted, powerstrip (1) is preferably suitable, according to any fashion known in theart, to provide power to multiple robotic devices. In that regard, eachrobotic device (20) is suitably equipped with a circuit breaker (notshown) in any fashion known in the art in order to isolate the roboticdevice (20) from the power strip (1) in the event that the roboticdevice short circuits. In such a manner, the failure of the entire powerstrip (1) is prevented.

Referring now to FIG. 3a, a simplified block diagram of a robotic devicefor use in an automated tape cartridge library according to the priorart is shown. As seen therein, a prior art robotic device (30) in anautomated tape cartridge library has a pair of spaced apart, oppositelycharged power rails (32). The robotic device (30) is provided with apair of brush contacts (34) for supplying power from two power rails(32) to the robotic device (30), in order to allow movement of therobotic device (30). As seen in FIG. 3a, the large distance, x, betweena cooperating pair of brushes (34) creates uneven wear on the brushes(34) due to construction tolerances in the robotic device (30) and thetrack or power rails (32). Brushes (34) also causes uneven drag on therobotic device (30) by creating a moment load resulting from theseparation, x, between the brush (34) and power rail (32) frictionpoints.

FIG. 3b is a simplified a block diagram of a robotic device for use inan automated tape cartridge library having brush and strip powerdistribution. As seen therein, in contrast to the prior artconfiguration of FIG. 3a, power is supplied to the robotic device (20)through the power strip (1) and brush (6) configuration described inconnection with FIGS. 1 and 2a-b, thereby facilitating the eliminationof the large separation between a pair of cooperating brushes (6A, 6B),and the accompanying problems, and allowing for lower constructiontolerance requirements. The single rail construction, two-sided powerstrip (1) and brush (6) configuration also acts to reduce costs andprovides for a more integrated assembly. As seen in FIG. 3b, anoptional, non-powered lower guide rail (36) may also be provided forrobotic device (20). It should also be noted that the copper foil tapethat may be used in the construction of the power strip (1) may beinstalled in the field during the assembly of the automated tapecartridge library. In such a fashion, it may be possible to eliminateall electrical joints in power strip (1) by using a continuous copperfoil strip.

FIGS. 4a and 4 b are simplified overhead block diagrams of a power strip(1) and robotic device (20) with conductive brushes (6) for use in anautomated tape cartridge libraries according to the present invention.As seen in FIG. 4a, power strips (1) may be fed power from both endsthereof, or multiple sections of power strips may be fed from both ends.Robotic device (20) is preferably provided with multiple pairs ofcooperating brush contacts (6), only the top brushes in each cooperatingpair being visible in FIG. 4a. In that regard, with reference again toFIGS. 2a and 2 b, it should also be noted that brush pairs on each sideof power strip (1) are oriented so as to follow the same path. That is,a pair of brushes (6) contacting the same conductive surface (1A, 1B)are aligned so that both such brushes (6) contact the same part of theconductive surface (1A, 1B) as robotic device (20) moves in the library.Such a brush orientation facilitates the creation of a beneficial oxidelayer on the conductive surfaces (1A, 1B). As will be discussed ingreater detail below, such an oxide layer helps reduce both electricaland sliding resistance between the brushes and the conductive surfaces(1A, 1B).

Referring still to FIGS. 4a and 4 b, cooperating brush pairs arepreferably spaced apart on robotic device (20). Such spacing, as well asthe use of multiple cooperating brush pairs provides for greaterrobustness and freedom of movement for robotic device (20) in the eventof track irregularities, including unevenness or “dead” track sections.In that regard, as seen in FIG. 4a, a non-powered or “dead” section (40)of power strip (1) will not necessarily prevent robotic device (20) fromtraversing the full extent of the power strip (1). That is, as therobotic device (20) moves across the dead track section (40), onecooperating pair of brushes always maintains contact with a poweredtrack section (42, 44). Similarly, as seen in FIG. 4b, power strip (1)may be fed power from a more centralized region thereof. As a result ofthe separation of cooperating pairs of brush contacts, robotic device(20) may be able to traverse longer distances than the length of powerstrip (1) onto and off of non-powered end-of-track sections (46, 48),provided at least one cooperating pair of brushes maintain contact withpowered track section (50). Moreover, in such a fashion, non-poweredtrack sections may be provided where a robotic device (20) may bedeliberately driven off power strip (1) and thereby powered down forservice.

In that same regard, FIGS. 4c and 4 d depict simplified electricalschematics of power supply redundancy schemes. As seen in FIG. 4c, in abrush and strip power distribution system, failure of a power supply(150) or a break (152) in the electrical continuity in a power strip (1)will cause a power interruption. Such an electrical discontinuity (152)in turn will result in a loss of power to all of the robotic devices(20i, 20ii, 20iii, 20iv) connected to the conductor. More specifically,such an electrical break (152) will result in the loss of power to thosedevices (20iii, 20iv) located on the disconnected side (154) of thestrip (1). As will be described in greater detail below, a brush a strippower distribution system may be implemented using many interconnectedsegments or sections to create power strip (1). Each interconnectsubstantially increases the possibility that power to part or all of thepower strip (1) may be interrupted.

The present design substantially improves the reliability of such apower distribution system by ensuring that the failure of a single powersupply or an electrical break in power strip (1) will not interruptoperation of the automated robotic library. More specifically, as seenin FIG. 4d, the present invention preferably provides for connecting twopower supplies (150i, 150ii), rather than one, to power strip (1). Inthe preferred embodiment shown in FIG. 4d, the two power supplies (150i,150ii) are positioned at the two ends of power strip (1), andelectrically connected to both ends of power strip (1). The powersupplies (150i, 150ii) are preferably of the redundant/load sharingtype.

When both supplies (150i, 150ii) are active and functioning normally,they share the load created by robotic devices (20i, 20ii, 20iii, 20iv)nearly equally. In the event, however, that one power supply (e.g.,150i) fails, the remaining power supply (e.g., 150ii) automaticallybegins to source power to all of the devices (20i, 20ii, 20iii, 20iv)connected to the power strip (1). Moreover, in the event of anelectrical discontinuity or break (152) in the power strip (1), eachpower supply (150i, 150ii) will continue to deliver power to the devices(20i, 20ii, 20iii, 20iv) located on that power supply's (150i, 150ii)respective side of the break (152). Alternatively, as shown in dashedline fashion in FIG. 4c, single power supply (150) may be configured tosupply power to both ends of power strip (1), thereby ensuring that abreak (152) in power strip (1) will not result in loss of power to anyof robotic devices (20i, 20ii, 20iii, 20iv). It should be noted thatwhile shown in FIGS. 4c and 4 d as electrically connected at the ends ofpower strip (1), power supplies (150, 150i, 150ii) may alternativelyand/or additionally be electrically connected to any other point orpoints on power strip (1). That is, in a power strip (1) comprising aplurality of electrically interconnected sections or segments, powersupplies (150, 150i, 150ii) may be electrically connected to any numberof sections anywhere along power strip (1). It should also be noted thatthe power supply redundancy schemes depicted in FIGS. 4c and 4 d areequally suitable for use in the brush and wheel power distributionsystem described in detail immediately below.

Referring next to FIGS. 5 through 8a and 8 b, various perspective, sideand cross-sectional views of a robotic device for use in an automatedtape cartridge library having brush and wheel power distribution. Asseen therein, in this alternative embodiment, robotic device (20) issupported by a guide rail (2), which is provided with a pair ofoppositely charged power conductors (3), preferably in the form ofcopper rails. Power rails (3) supply power to robotic device (20)through power transmission carriage assembly (4). Power supplied torobotic device (20) via power rails (3) and power transmission carriage(4) powers a motor (not shown), which in turn drives belt and gearmechanism (22) to permit robotic device (20) to move back and forthalong guide rail (2) via guide wheels (26). In that regard, it should benoted that power rails (3) may provide either AC or DC power to roboticdevice (20). It should also be noted again that while only a singlerobotic device (20) is depicted, power rails (3) are preferablysuitable, according to any fashion known in the art, to provide power tomultiple robotic devices. As described above in connection with thebrush and stip power distribution, each robotic device (20) is suitablyequipped with a circuit breaker (not shown) in any fashion known in theart in order to isolate the robotic device (20) from the power rails (3)in the event that the robotic device short circuits. In such a manner,the failure of the power rails (3) is prevented.

Power transmission carriage (4) includes multiple cooperating pairs ofconduction wheels (5) (preferably copper), the individual members of acooperating pair provided in contact, respectively, with oppositelycharged conductor rails (3). Conductive brushes (10) are provided tocontact conduction wheels (5) and are spring loaded (11), preferablyindependently, to maintain such contact. To maintain contact betweenconduction wheels (5) and conductor rails (3), power transmissioncarriage (4) also includes vertical pre-load spring (6). Powertransmission carriage (4) still further includes gimbal arm (7) withpivot shaft (8) and pivot screw (9) for carriage compliance. Once again,multiple or redundant conduction wheel (5) and conductive brush (10)pairs are preferably provided, and preferably spring loaded (11)independently, to improve robustness and reliability in the event of abrush failure, momentary loss of contact at one or more wheels due toany track irregularities, including seams or joints therein, or voltageirregularities between adjacent power rails (3). In that same regard,while a single vertical pre load spring (6) is shown, each conductionwheel (5) could also be independently spring loaded to maintain contactwith conductor rails (3), thereby allowing for better negotiation of anytrack irregularities or imperfections, including joints or seams.

The brush and wheel embodiment can reduce particulate generation whichmay accompany the brush and power strip embodiment as a result ofbrushes negotiating imperfectly aligned track joints. Moreover, becauseof the more contained nature of the contact between a brush and wheel asopposed to between a brush and extended power stip, any such particulategeneration can be more easily contained in the brush and wheelembodiment, such as through the use of a container (not shown)surrounding the brush and wheel to capture any particulate. The brushand wheel embodiment also provides for improved negotiation of joints bya robotic device as it provides for wheels rolling rather than brushessliding over a joint. As a result, less strict tolerances are requiredfor joint design and assembly. Moreover, a brush passing over anirregularity in a power strip, such as a joint, scrapes both the brushand the track, causing wear to both. A wheel can more easily negotiatesuch irregularities, thereby reducing such wear.

The brush and wheel embodiment also provides for reduced electrical andsliding resistance as compared to the brush and stip embodiment. In thatregard, a beneficial oxide layer that reduces both electrical andsliding resistance develops more easily and quickly between a brush andwheel contact than between a brush and extended power strip contact,again because of the more contained nature of the contact. That is, fora given linear movement of a robotic device, a brush covers much more ofthe surface, and much of the same surface of a wheel than it covers onan extended linear conductive strip. This is particularly advantageousin reducing high brush resistance when the robotic device is travelingat low speeds.

The brush and wheel embodiment also generally reduces the spring loadingforces required. In that regard, because of irregularities in aconductive strip, such as due to joints or seams, a high spring loadingforce is required to ensure contact is maintained between a brush andpower strip, particularly over time as the brush wears. In contrast,with a brush and wheel, there are no irregularities in the point ofcontact between the brush and wheel. As a result, the spring force usedto maintain contact between the brush and wheel can be reduced, whichalso reduces the drive force or power necessary to move the roboticdevice.

Still further, the brush and wheel embodiment also reduces track wear,since the rolling friction between the wheel and track creates less wearthan the sliding friction between a brush and power strip. In thatregard, the conductive strips in a brush and power strip embodiment mustbe made sufficiently thick to allow for wear due to brush contact overtime. Moreover, as previously noted, spring loading forces for brushesin a brush and power strip embodiment must be sufficiently high toensure contact is maintained between the brush and power strip over timeas both wear. A brush and wheel embodiment eliminates these concerns andallows for the use of a more inexpensive track having less stringentdesign and assembly tolerances.

In either of the brush and power strip or brush and wheel embodiments,the power strip or conduction rails may be oriented horizontally, asshown in the Figures, or vertically, or in a combination of both.Indeed, a vertical track orientation may be preferred, particularly forcurved track areas. In that regard, for example, an extended printedcircuit board power strip of the type previously described can be easilybent to follow a curved track area if such a power strip is providedwith a vertical orientation. In contrast, to follow a curved track witha such a power strip oriented horizontally, a curved printed circuitboard may need to be specially manufactured. Moreover, as the radius ofcurvature of a curved track area decreases, skidding and wear of wheelsincreases on a horizontally oriented track. This can be alleviated by avertically oriented track.

Again in either embodiment, the power conductors or strips may beprovided in segments or sections that can be electrically connectedtogether in a modular fashion, thereby extending the power conductors orstrip substantially throughout a data storage library. Such sections maybe joined together along the path or a guide rail on which a roboticdevice moves in the library. In that regard, it should be noted that ineither embodiment, the segments or sections of power conductors orstrips may be connected in an end to end fashion to provide for roboticdevice movement in a single dimension, or may be connected in agrid-like fashion to provide for robotic device movement in twodimensions and/or to provide power across multiple horizontal paths forrobotic devices, which paths may be stacked vertically on top of eachother, thereby providing for robotic device access to multiple mediacartridge storage cells arranged in a two dimensional configuration ofmultiple rows and columns, such as a planar “wall” or “floor,” or acurved or substantially cylindrical “wall.” Still further, again ineither embodiment, the segments or sections of power conductors orstrips may be connected in such a fashion as to provide for roboticdevice movement in three dimensions.

When used in such a fashion for power distribution, segmented powerstrips will be sensitive to alignment so as not to create a sloppyjoint. A mis-aligned joint in the power strip may cause a brush to losecontact with a power strip due to bounce. Wear on the brushes and powerstrip pieces at the joints may also cause limited life of the joint.

As a result, a joint for such power strips is pre-loaded andoverconstrained to cause the power strips in the robot guide rail tosubstantially align. Such a joint preferably includes conductorsslightly longer than the supporting structure of the robot guide rail,so as to force adjoining conductors into contact at their ends as guiderails and conductors are assembled. In addition, adjoining ends ofconductors are preferably beveled or angled such that a force urging theconductors together causes the conductors to slip laterally against eachother, so as to again facilitate alignment at the joint. Such a bevel orangle also spreads out the wiping action of a brush as it traverses thejoint, thereby prolonging the life of the joint and brush, and limitingany problems that may arise as a result of any small offset. Stillfurther, the power strips are preferably pre-loaded or biased by aspring load, thereby causing the joint to stay in compression for thelife of the joint.

In that regard, referring next to FIGS. 9 through 12a-g, variousperspective, cross-sectional and side views of a power strip and guiderail for use in an automated tape cartridge library. As previouslydescribed, power strip sections in a brush and power strip embodimentmay be sensitive to alignment. As seen in FIGS. 9-12g, guide railsections (2A, 2B) are designed to accept substantially planar, elongatedpower strip sections (1A, 1B). In that regard, power strip sections (1A,1B) are preferably of the printed circuit board type previouslydescribed, and preferably include upper (56) and lower (not shown)copper conductive layers on opposite surfaces of an FR4 type substratematerial (58). Track alignment pins (50) and holes (52) in guide railsections (2A, 2B) ensure that guide rails sections (2A, 2B) are properlyaligned at the joint, and a joint bolt (54) is provided to ensuresufficient force to maintain the joint. In that regard, an alternativelatch mechanism (55) is depicted in FIGS. 11a and 11 b to providesufficient force to maintain the joint.

Power strips (1A, 1B) are preferably beveled or angled (preferably at30°) in a complimentary fashion at adjoining ends so that such ends willmove or slide laterally relative to each other in the X-Y plane duringassembly of the joint, thereby accounting for varying tolerances in thelengths of adjoining power strips (1A, 1B) and/or guide rails (2A, 2B).In that same regard, power strips (1A, 1B) are preferably each providedwith spring arms (60), which act as means for biasing power strips (1A,1B) together against such lateral motion. Spring arms (60) preferablyinclude mounting pin holes (62) formed therein, which are designed toalign with similar mounting pin holes (64) formed in guide rails (2A,2B) for receipt of mounting pins (66). Such a configuration facilitatesthe previously described relative lateral motion between power strips(1A, 1B) in the X-Y plane during assembly, and helps to ensure thatpower strips (1A, 1B) remain in contact after assembly. A similar springarm, mounting pin hole and mounting pin arrangement (67) is preferablyprovided in a central region of each power strip (1) and guide rail (2)section (see FIG. 12e).

Power strips (1A, 1B) are also preferably provided at their adjoiningends complimentary tongue-and-groove like or dove tail type mating edgesor surfaces. Such edges, preferably formed with 45° angles, ensure thatpower strips (1A, 1B) remain co-planer at the joint (i.e., refrain frommovement relative to each other in the Z direction) so as not to exposean edge of an upper (56) or lower (not shown) conductive layer.Electrical connection is provided at the joint through the use of quickconnect electrical slide type connectors (3A, 3B). In that regard, upper(56) and lower (not shown) conductive layers of adjoining power strips(1A, 1B) each preferably include an electrical connection point. Uponassembly of power strips (1A, 1B), such electrical connection points areproximate each other such that one connector (3A) creates an electricalconnection between upper conductive layers (56) of adjoining powerstrips (1A, 1B, while the other connector (3B) creates an electricalconnection between lower conductive layers (not shown) of adjoiningpower strips (1A, 1B).

In such a fashion, power strips (1A, 1B) are assembled to create a jointwhere their respective conductive layers are proximate such that arobotic device having brush or wiper type contacts as previouslydescribed maintains electrical contact therewith as the robotic devicetraverses the joint. A well aligned power strip and guide rail joint isthus provided which facilitates easy movement of a brush or wipercontact thereacross, while at the same time accounting for differingmanufacturing tolerances and expansion rates between the dissimilarmaterials used in the power strips (1) and guide rails (2). It shouldalso be noted that while depicted in the figures in conjunction withprinted circuit type power strips (1), such features may be used withany type of power strip (1) previously described, or with any other typeof joint for power conductors, such as a single conductive strip or busbar. Indeed, many of the above features may also be used with any typeof joint, such as between guide rails without power.

As is well known in the art, robotic devices in an automated tapecartridge library must be able to communicate with a host controller.This is typically done using multiple conductors (three or more)including power, ground, and signal(s), which can cause many of the samecabling problems previously described. The relatively high cost and lowreliability of conductors and connectors pose a problem for implementinghigh reliability, low cost automated robotic data storage libraries.Such a problem is particularly troublesome if the space available forrouting such conductors is limited.

Such problems can be overcome by using the oppositely charged conductivelayers of a power strip, power rails, or a cable pair to supply not onlypower to the robotic devices, but communication signals between therobotic devices and a controller as well. In that regard, in a brush andpower strip embodiment, multiple conductors are particularly problematicwhen power and communication signals need to be sent to robotic devicesvia the power strip and brushes. Since the reliability of the electricalconnections in such an embodiment is inherently relatively low, asubstantial reliability and complexity penalty may be incurred whenmultiple conductors are used.

According to the present invention, a smaller, lower cost and higherreliability system is made possible by eliminating all conductors exceptthose absolutely needed: power and ground. Information which wouldotherwise be communicated via dedicated signal conductors is insteadmodulated onto the power conductor. In such a fashion, the communicationsignals share the same conductor that is used to power the roboticdevice. Modulator circuits on a controller and the robotic devicesencode the data from the eliminated conductors and impress a modulatedsignal onto the power conductor. Demodulator circuits on both endsreceive and recover the communication signals, translating the data backinto its original form. High-speed full-duplex communication is thusimplemented without the need for more than two conductors connecting thecontroller and the remote robotic devices.

Referring now to FIG. 13, a simplified block diagram illustratingdistribution of communication signals to and from robotic devices (72,74) for use in an automated tape cartridge library according to thepresent invention is shown. As seen therein, a power supply (70)provides power to robotic devices (72, 74) via power and groundconductors (76, 78), which are preferably the oppositely chargedconductive layers of a power strip as described in detail above. Acontroller (80), using processor and logic circuits (82), generatessignals for use in controlling the movement and operations of roboticdevices (72, 74). Controller (80) is also provided withmodulator/demodulator circuitry (84) to encode such communicationsignals and impress or superimpose such signals onto the power signalprovided to the robotic devices (72, 74) via the power conductors (76,78). Similar modulator/demodulator circuitry (84) is provided onboardrobotic devices (72, 74) to recover and decode the signals fromcontroller (80). Once recovered and decoded, such signals aretransmitted to motion controller circuitry (86) onboard robotic devices(72, 74) in order to effect the desired movement and operation of therobotic devices (72, 74).

Robotic devices (72, 74) communicate with controller (80) in the samefashion, thereby providing feedback to the controller (80) concerningmovement and operation of the robotic devices (72, 74), whichinformation the controller (80) may use to generate further controlsignals. As is readily apparent, then, processor and logic circuits(82), and modulator/demodulator circuitry (84) provide means forgenerating the communication signals for transmission between thecontroller (80) and the robotic devices (72, 74) on one of theconductors (76, 78).

In that regard, such communication signals may be combined with thepower signal in any fashion known in the art. For example, because powersignals are typically lower frequency signals, communication signals maycomprise higher frequency signals so that the power signal may befiltered out by robotic devices (72, 74) and controller (80) usinghigh-pass filters to thereby recover the communication signals. In sucha fashion, high-speed full duplex communication may be implementedbetween the controller (80) and robotic devices (72, 74) without theneed for multiple conductors, cabling, or wireless connection.

Electromagnetic interference and unintended signal emissions can be aproblem when transmitting communication signals between robotic devicesand a controller using the oppositely charged conductive layers of apower strip as described above. This can be particularly true for powerconductors that are quite long. Interference from radio, television, andother radio frequency (RF) electromagnetic radiation sources, whether ornot intentionally emitted, can interfere with the communication signalsmodulated onto the power conductors. Such interference can cause datatransmission errors and slow the maximum attainable rate of datatransfer.

In that same regard, when communication signals are modulated onto along power conductor, some of the RF energy can radiate through the airand interfere with nearby independent power conductors. If the nearbypower conductors also contain modulated communication signals, harmfulinterference can result. The energy radiated by the modulated powerconductors may also cause interference in radio and television broadcastbands, or other restricted RF bands. Such interference may be prohibitedby government regulations.

According to the present invention, the electromagnetic compatibility(EMC) of the brush and power strip embodiment of the present inventionis improved by the orientation of the power strip conductors. As will bedescribed in greater detail below, positive and negative (ground)conductors are preferably separated by a thin layer of insulatingdielectric. The positive conductor is preferably centered over thenegative conductor. The negative conductor is preferably made wider thanthe positive conductor in order to minimize fringing of the electricfiled due to the modulated communication signal. The thin dielectricminimizes the “loop area” of the conductors. The conductors themselvesare flat and relatively thin in order to reduce their respective surfaceareas, thereby reducing “skin effect.” All of the above features serveto improve the EMC of the brush and power strip embodiment.

Referring next to FIGS. 14 and 15, cross-sectional and top views of thepower strip for use in an automated tape cartridge library according tothe present invention are shown. As seen therein, one conductive layer(56), which is shown in the figures as positively charged or a powerconductor, is preferably provided with a narrower width, w₁, than thewidth, w₂, of the other conductive layer (57), which is shown in thefigures as negatively charged or a ground conductor. A thin dielectricmaterial (58) is provided between conductive layers (56, 57), and has awidth, w₂, that is preferably substantially equal to that of conductivelayer (57). While not required, conductive layer (56) is preferablycentered on the surface of one side of dielectric material (58) relativeto the width, w₂, of conductive layer (57), and thus at equal distances,x, from the edges of dielectric material (58) since dielectric material(58) has substantially the same width, w₂, as conductive layer (57). Inthat regard, as previously described, conductive layers (56, 57) arepreferably copper. Dielectric material (58) preferably has a lowdielectric constant, k, such as FR4 previously described, or Teflon.

The above-described configuration serves to improve the electromagneticcompatibility (EMC) of the power strip. More particularly, the differentwidths of the conductive layers (56, 57) help to minimize fringing ofthe electric field due to the modulated communication signals. In thatregard, the greater the distance x can be made, either by narrowingconductive layer (56) or by widening conductive layer (57) anddielectric (58), the greater the beneficial effect on fringing.Conductive layers (56, 57) should, however, maintain sufficient width toallow adequate contact with brushes (6) in order to supply power to arobotic device.

Moreover, as is well known in the art, electrical current is generallyforced to the outside surfaces of a conductor, particularly at higherfrequencies. Conductors having less surface area therefore have higherresistance, a phenomenon generally referred to as “skin effect.” Bymaking conductive layers (56, 57) generally flat and thin, more surfacearea is created, thereby reducing resistance for the higher frequencycommunication signals. Such lowered resistance in turn reduced signalloss, thereby allowing for the use of longer tracks, while at the sametime improving signal integrity by providing better immunity frominterference by other signals.

Still further, a thin dielectric (58) helps to minimize the “loop area”of the conductors (56, 57). In that regard, FIGS. 16a and 16 b are across-sectional view and a simplified electrical schematic,respectively, of the power strip for use in an automated tape cartridgelibrary according to the present invention. As seen therein, conductors(56, 57) are connected through a power supply (90) and a load (92),thereby creating a loop. While the length, l, of conductors (56, 57) isgenerally fixed, the thickness, t, of the dielectric (58) therebetweenmay be adjusted. That is, while the length of the loop is generallyfixed, its height is adjustable. A thin dielectric (58) thus helps toreduce “loop area.”

As previously noted, by minimizing fringing, “skin effect” and “looparea,” the above-described configuration improves electromagneticcompatibility (EMC). In general, the above-described power rail presentsa low impedance, thereby reducing coupling from interfering signals. Inparticular, minimizing FL fringing reduces the possibility that acommunication signal on a power rail will interfere with other devices,including other power rails carrying other communication signals.Minimizing “skin effect” and “loop area” also reduces the possibility ofsuch radiation type interference.

In a power line communication system such as described above, signalreflections can pose a significant signal integrity problem. Reflectionscan destructively interfere with the communication signal, particularlywhen the length of the power line is long compared to the wavelength ofthe carrier signal. The reflection problem can be mitigated with theaddition of line terminators at the extreme ends of the power line. Inthat regard, FIG. 17 is a simplified electrical schematic diagramillustrating a termination scheme for a line in a power strip or railcommunication system according to the present invention. As seentherein, the termination scheme comprises two parallel terminators (90,91) at each of the two ends of the power line/rail (92). As shown inFIG. 17, each terminator (90, 91) preferably comprises an RCtermination, although those of ordinary skill will appreciate that avariety of termination schemes could be employed to achieve the sameeffect.

Still referring to FIG. 17, series terminators (93, 94), which arepreferably resistors, are also preferably provided on the output of eachmodulator circuit (95) for both the controller (96) and the automatedrobot, or handbot (97). The combination of series termination andparallel termination further enhances the signal integrity of the powerline (92). Either series or parallel termination could be used on itsown, however. Proper line termination such as that depicted in FIG. 17dramatically improves signal integrity and increases the maximumattainable rate of data transfer as well as extending the maximum lengthof the conductors.

Referring now to FIG. 18, a simplified, exemplary flowchart of themethod of the present invention is shown, denoted generally by referencenumeral 100. The method (100) is provided for use in a data storagelibrary having a plurality of cells for holding media cartridges for usein storing data, at least one media drive, a robotic device fortransporting cartridges between the plurality of cells and the at leastone media drive in the data storage library, and a controller forcontrolling the robotic device, a method for transmission ofcommunication signals between the controller and the robotic device. Asseen in FIG. 18, the method (100) comprises providing (102) asubstantially planar electrical insulator having opposed first andsecond sides, providing (104) a first substantially planer electricalconductor on the first side of the insulator for use in providingelectrical power to the robotic device, the first conductor to beprovided with an electrical charge and having a width, and providing(106) a second substantially planar electrical conductor on the secondside of the insulator for use in providing electrical power to therobotic device, the second conductor to be provided with an electricalcharge opposite the electrical charge of the first conductor, the secondconductor having a width. The method further comprises providing (108)means for generating the communication signals for transmission betweenthe controller and the robotic device on one of the first and secondconductors, wherein the width of the second conductor is less than thewidth of the first conductor, and the second conductor is substantiallycentered on the second side of the insulator relative to the width ofthe first conductor to reduce fringing of an electromagnetic fieldresulting from a transmitted communication signal.

It should be noted that the simplified flowchart depicted in FIG. 18 isexemplary of the method of the present invention. In that regard, thesteps of such method may be executed in sequences other than those shownin FIG. 18, including the execution of one or more steps simultaneously.

Thus it is apparent that the present invention provides for improvedsystem and method for transmitting communication signals between acontroller and a robotic device in a data storage library. As is readilyapparent from the foregoing description, the system and method of thepresent invention improve the electromagnetic compatibility (EMC) ofbrush and strip power distribution by the orientation of the power stripconductors. More particularly, the system and method of the presentinvention employ positive and negative (ground) conductors preferablyseparated by a thin layer of insulating dielectric. The positiveconductor is preferably centered over the negative conductor, and thenegative conductor is preferably wider than the positive conductor inorder to reduce fringing of the electric filed due to the modulatedcommunication signal. The thin dielectric reduces the “loop area” of theconductors. The conductors themselves are substantially flat andrelatively thin in order to reduce their respective surface areas,thereby reducing “skin effect.”

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

What is claimed is:
 1. In a data storage library having a plurality ofcells for holding media cartridges for use in storing data, at least onemedia drive, a robotic device for transporting cartridges between theplurality of cells and the at least one media drive in the data storagelibrary, and a controller for controlling the robotic device, a systemfor transmission of communication signals between the controller and therobotic device, the system comprising: a substantially planar electricalinsulator having opposed first and second sides; a first substantiallyplanar electrical conductor on the first side of the insulator for usein providing electrical power to the robotic device, the first conductorto be provided with an electrical charge and having a width; a secondsubstantially planar electrical conductor on the second side of theinsulator for use in providing electrical power to the robotic device,the second conductor to be provided with an electrical charge oppositethe electrical charge of the first conductor, the second conductorhaving a width; and means for generating the communication signals fortransmission between the controller and the robotic device on one of thefirst and second conductors, wherein the width of the second conductoris less than the width of the first conductor, and the second conductoris substantially centered on the second side of the insulator relativeto the width of the first conductor to reduce fringing of anelectromagnetic field resulting from a transmitted communication signal.2. The system of claim 1 wherein each of the first and second conductorscomprises an elongated conductive strip, and the insulator comprises anelongated member provided with a thickness sufficient to minimize a looparea associated with the elongated first and second conductors.
 3. Thesystem of claim 2 wherein the first and second conductors and theinsulator together comprise a power distribution strip, and wherein aplurality of power distribution strips are electrically connected fortransmission of electrical power and communication signals substantiallythroughout the data storage library to the robotic device.
 4. The systemof claim 3 wherein the plurality of electrically connected power stripshas an end point, the end point being provided with a terminator inelectrical communication with the plurality of electrically connectedpower strips for reducing reflection of the transmitted communicationsignals, the terminator comprising a resistor and capacitor.
 5. Thesystem of claim 3 wherein the robotic device is provided with electricalcontacts for making sliding electrical contact with the first and secondconductors.
 6. The system of claim 1 wherein the communication signalscomprise high frequency signals, and the first and second conductors areprovided a surface area sufficient to reduce a skin effect associatedwith the transmission of the high frequency communication signals. 7.The system of claim 6 wherein the means for generating the communicationsignals comprises modulator/demodulator circuitry associated with thecontroller, and modulator/demodulator circuitry provided on the roboticdevice, the modulator/demodulator circuitry for encoding andtransmitting communication signals on one of the first and secondconductors and for receiving and decoding transmitted communicationsignals.
 8. The system of claim 7 wherein the first and secondconductors are for transmitting a power signal to the robotic device,the power signal having a lower frequency than the high frequencycommunication signals, and wherein the modulator/demodulator circuitrycomprises a high-pass filter for recovering the high frequencycommunication signals from the lower frequency power signal.
 9. Thesystem of claim 1 wherein the insulator comprises a material having alow dielectric constant.
 10. The system of claim 1 wherein each of thefirst and second conductors comprises copper.
 11. In a data storagelibrary having a plurality of cells for holding media cartridges for usein storing data, at least one media drive, a robotic device fortransporting cartridges between the plurality of cells and the at leastone media drive in the data storage library, and a controller forcontrolling the robotic device, a system for transmission ofcommunication signals between the controller and the robotic device, thesystem comprising: a substantially planar electrical insulator havingopposed first and second sides; a first substantially planar electricalconductor on the first side of the insulator for use in providingelectrical power to the robotic device, the first conductor to beprovided with an electrical charge and having a width; a secondsubstantially planar electrical conductor on the second side of theinsulator for use in providing electrical power to the robotic device,the second conductor to be provided with an electrical charge oppositethe electrical charge of the first conductor, the second conductorhaving a width; and means for generating the communication signals fortransmission between the controller and the robotic device on one of thefirst and second conductors, wherein each of the first and secondconductors comprises an elongated conductive strip, and the insulatorcomprises an elongated member provided with a thickness sufficient tominimize a loop area associated with the elongated first and secondconductors.
 12. In a data storage library having a plurality of cellsfor holding media cartridges for use in storing data, at least one mediadrive, a robotic device for transporting cartridges between theplurality of cells and the at least one media drive in the data storagelibrary, and a controller for controlling the robotic device, a methodfor transmission of communication signals between the controller and therobotic device, the method comprising: providing a substantially planarelectrical insulator having opposed first and second sides; providing afirst substantially planar electrical conductor on the first side of theinsulator for use in providing electrical power to the robotic device,the first conductor to be provided with an electrical charge and havinga width; providing a second substantially planar electrical conductor onthe second side of the insulator for use in providing electrical powerto the robotic device, the second conductor to be provided with anelectrical charge opposite the electrical charge of the first conductor,the second conductor having a width; and providing means for generatingthe communication signals for transmission between the controller andthe robotic device on one of the first and second conductors, whereinthe width of the second conductor is less than the width of the firstconductor, and the second conductor is substantially centered on thesecond side of the insulator relative to the width of the firstconductor to reduce fringing of an electromagnetic field resulting froma transmitted communication signal.
 13. The method of claim 12 whereineach of the first and second conductors comprises an elongatedconductive strip, and the insulator comprises an elongated memberprovided with a thickness sufficient to minimize a loop area associatedwith the elongated first and second conductors.
 14. The method of claim13 wherein the first and second conductors and the insulator togethercomprise a power distribution strip, and wherein a plurality of powerdistribution strips are electrically connected for transmission ofelectrical power and communication signals substantially throughout thedata storage library to the robotic device.
 15. The method of claim 14wherein the plurality of electrically connected power strips has an endpoint, the end point being provided with a terminator in electricalcommunication with the plurality of electrically connected power stripsfor reducing reflection of the transmitted communication signals, theterminator comprising a resistor and capacitor.
 16. The method of claim14 wherein the robotic device is provided with electrical contacts formaking sliding electrical contact with the first and second conductors.17. The method of claim 12 wherein the communication signals comprisehigh frequency signals, and the first and second conductors are provideda surface area sufficient to reduce a skin effect associated with thetransmission of the high frequency communication signals.
 18. The methodof claim 17 wherein the means for generating the communication signalscomprises modulation/demodulation circuitry associated with thecontroller, and modulator/demodulator circuitry provided on the roboticdevice, the modulator/demodulator circuitry for encoding andtransmitting communication signals on one of the first and secondconductors and for receiving and decoding transmitted communicationsignals.
 19. The method of claim 18 wherein the first and secondconductors are for transmitting a power signal to the robotic device,the power signal having a lower frequency than the high frequencycommunication signals, and wherein the modulator/demodulator circuitrycomprises a high-pass filter for recovering the high frequencycommunication signals from the lower frequency power signal.
 20. Themethod of claim 12 wherein the insulator comprises a material having alow dielectric constant.
 21. The method of claim 12 wherein each of thefirst and second conductors comprises copper.
 22. In a data storagelibrary having a plurality of cells for holding media cartridges for usein storing data, at least one media drive, a robotic device fortransporting cartridges between the plurality of cells and the at leastone media drive in the data storage library, and a controller forcontrolling the robotic device, a method for transmission ofcommunication signals between the controller and the robotic device, themethod comprising: providing a substantially planar electrical insulatorhaving opposed first and second sides; providing a first substantiallyplanar electrical conductor on the first side of the insulator for usein providing electrical power to the robotic device, the first conductorto be provided with an electrical charge and having a width; providing asecond substantially planar electrical conductor on the second side ofthe insulator for use in providing electrical power to the roboticdevice, the second conductor to be provided with an electrical chargeopposite the electrical charge of the first conductor, the secondconductor having a width; and providing means for generating thecommunication signals for transmission between the controller and therobotic device on one of the first and second conductors, wherein eachof the first and second conductors comprises an elongated conductivestrip, and the insulator comprises an elongated member provided with athickness sufficient to minimize a loop area associated with theelongated first and second conductors.
 23. In a data storage libraryhaving a plurality of cells for holding media cafiridges for use instoring data, at least one media drive, a robotic device fortransporting cartridges between the plurality of cells and the at leastone media drive in the data storage library, and a controller forcontrolling the robotic device, a system for transmission ofcommunication signals between the controller and the robotic device, thesystem comprising: an electrical insulator having first and secondsides; a first electrical conductor on the first side of the insulatorfor use in providing electrical power to the robotic device, the firstconductor having a width; a second electrical conductor on the secondside of the insulator for use in providing electrical power to therobotic device, the second conductor having a width; and a signalgenerator for generating the communication signals for transmissionbetween the controller and the robotic device on one of the first andsecond conductors, wherein the width of the second conductor is lessthan the width of the first conductor, and the second conductor issubstantially centered on the second side of the insulator relative tothe width of the first conductor to reduce fringing of anelectromagnetic field resulting from a transmitted communication signal.24. The system of claim 23 wherein each of the first and secondconductors comprises an elongated conductor, and the insulator isprovided with a thickness sufficient to minimize a loop area associatedwith the elongated first and second conductors.
 25. The system of claim23 wherein the first and second conductors and the insulator togethercomprise a power distributor, and wherein a plurality of powerdistributors are electrically connected for transmission of electricalpower and communication signals substantially throughout the datastorage library to the robotic device.
 26. The method of claim 25wherein the plurality of electrically connected power distributors hasan end point, the end point being provided with a terminator inelectrical communication with the plurality of electrically connectedpower
 27. The system of claim 25 wherein the robotic device is providedwith electrical contacts for making electrical contact with the firstand second conductors.
 28. The system of claim 23 wherein thecommunication signals comprise high frequency signals, and the first andsecond conductors are provided a surface area sufficient to reduce askin effect associated with the transmission of the high frequencycommunication signals.
 29. The system of claim 28 wherein the signalgenerator for generating the communication signals comprisesmodulator/demodulator circuitry associated with the controller, andmodulator/demodulator circuitry provided on the robotic device, themodulator/demodulator circuitry for encoding and transmittingcommunication signals on one of the first and second conductors and forreceiving and decoding transmitted communication signals.
 30. The systemof claim 29 wherein the first and second conductors are for transmittinga power signal to the robotic device, the power signal having a lowerfrequency than the high frequency communication signals, and wherein themodulator/demodulator circuitry comprises a high-pass filter forrecovering the high frequency communication signals from the lowerfrequency power signal.
 31. The system of claim 23 wherein the insulatorcomprises a material having a low dielectric constant.
 32. The system ofclaim 23 wherein each of the first and second conductors comprisescopper.
 33. In a data storage library having a plurality of cells forholding media cartridges for use in storing data, at least one mediadrive, a robotic device for transporting cartridges between theplurality of cells and the at least one media drive in the data storagelibrary, and a controller for controlling the robotic device, a systemfor transmission of communication signals between the controller and therobotic device, the system comprising: an elcetrical insulator havingfirst and second sides; a first electrical conductor on the first sideof the insulator for use in providing electrical power to the roboticdevice; a second electrical conductor on the second side of theinsulator for use in providing electrical power to the robotic device;and a signal generator for generating the communication signals fortransmission between the controller and the robotic device on one of thefirst and second conductors, wherein each of the first and secondconductors comprises an elongated conductor, and the insulator isprovided with a thickness sufficient to minimize a loop area associatedwith the elongated first and second conductors.
 34. The system of claim33 wherein the first and second conductors and the insulator togethercomprise a power distributor, and wherein a plurality of powerdistributors are electrically connected for transmission of electricalpower and communication signals substantially throughout the datastorage library to the robotic device.
 35. The method of claim 34wherein the plurality of electrically connected power distributors hasan end point, the end point being provided with terminator in electricalcommunication with the plurality of electrically connected powerdistributors for reducing reflection of the transmitted communicationsignals.
 36. The system of claim 34 wherein the robotic device isprovided with electrical contacts for making electrical contact with thefirst and second conductors.
 37. The system of claim 33 wherein thecommunication signals comprise high frequency signals, and the first andsecond conductors are provided a surface area sufficient to reduce askin effect associated with the transmission of the high frequencycommunication signals.
 38. The system of claim 37 wherein the signalgenerator for generating the communication signals comprisesmodulator/demodulator circuitry associated with the controller, andmodulator/demodulator circuitry provided on the robotic device, themodulator/demodulator circuitry for encoding and transmittingcommunication signals on one of the first and second conductors and forreceiving and decoding transmitted communication signals.
 39. The systemof claim 38 wherein the first and second conductors are for transmittinga power signal to the robotic device, the power signal having a lowerfrequency than the high frequency communication signals, and wherein themodulator/demodulator circuitry comprises a high-pass filter forrecovering the high frequency communication signals from the lowerfrequency power signal.
 40. The system of claim 33 wherein the insulatorcomprises a material having a low dielectric constant.
 41. The system ofclaim 33 wherein each of the first and second conductors comprisescopper.
 42. In a data storage library having a plurality of cells forholding media cartridges for use in storing data, at least one mediadrive, a robotic device for transporting cartridges between theplurality of cells and the at least one media drive in the data storagelibrary, and a controller for controlling the robotic device, a systemfor transmission of communication signals between the controller and therobotic device, the system comprising: first and second electricalconductors distributed in the data storage library for use in providingelectrical power to the robotic device, wherein the robotic device isconfigured to make moving electrical contact with the first and secondelectrical conductors as the robotic device travels in the data storagelibrary; an insulator for separating the first and second electricalconductors, wherein communication signals are to be transmitted betweenthe controller and the robotic device on one of the first and secondconductors, and the first and second conductors and the insulator areconfigured to reduce fringing of an electromagnetic field resulting froma transmitted communication signal.
 43. In a data storage library havinga plurality of cells for holding media cartridges for use in storingdata, at least one media drive, a robotic device for transportingcartridges between the plurality of cells and the at least one mediadrive in the data storage library, and a controller for controlling therobotic device, a system for transmission of communication signalsbetween the controller and the robotic device, the system comprising:first and second electrical conductors distributed in the data storagelibrary for use in providing electrical power to the robotic device,wherein the robotic device is configured to make moving electricalcontact with the first and second electrical conductors as the roboticdevice travels in the data storage library; an insulator for separatingthe first and second electrical conductors, wherein conmwnicationsignals are to be transmitted between the controller and the roboticdevice on one of the first and second conductors, and the first andsecond conductors and the insulator are configured to reduce a loop areaassociated with the first and second conductors.
 44. In a data storagelibrary having a plurality of cells for holding media cartridges for usein storing data, at least one media drive, a robotic device fortransporting cartridges between the plurality of cells and the at leastone media drive in the data storage library, and a controller forcontrolling the robotic device, a system for transmission ofcommunication signals between the controller and the robotic device, thesystem comprising: first and second electrical conductors distributed inthe data storage library for use in providing electrical power to therobotic device, wherein the robotic device is configured to make movingelectrical contact with the first and second electrical conductors asthe robotic device travels in the data storage library; an insulator forseparating the first and second electrical conductors, whereincommunication signals are to be transmitted between the controller andthc robotic device on one of the first and second conductors, and thefirst and second conductors are provided surface area sufficient toreduce a skin effect associated with the transmission of thecommunication signals.